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Optimization of low-head, dam-toe, small hydropowerprojects
S. K. Singal,1,a R. P. Saini,1 and C. S. Raghuvanshi21Alternate Hydro Energy Centre, Indian Institute of Technology Roorkee, Roorkee,
Uttarakhand 247667, India2Department of Water Resources Development and Management, Indian Institute of
Technology Roorkee, Roorkee, Uttarakhand 247667, India
Received 12 January 2010; accepted 27 June 2010; published online 5 August 2010
In most developing countries, such as India, there exists a large amount of hydro-
power potential. This is especially true in the small hydro plant capacity range of
up to 25 MW. Only a small fraction of this potential has been tapped so far, perhaps
due to higher per kilowatt installation cost as compared to large hydro. Small
hydropower sites can be classified as i run-of-river; ii canal based, and iii
dam-toe schemes, depending on their location. Dam-toe schemes need low invest-
ment and can be developed in a shorter period of time. In the present study, an
attempt has been made to estimate the cost of the low-head, dam-toe, small hydro-power schemes. A methodology for cost optimization of such schemes has been
developed considering the quantities of various items for each component of the
scheme and prevailing prices. Further, to determine financial viability of the
scheme at different load factors, sensitivity analysis has also been carried out. It has
been found that low-head, dam-toe, small hydropower schemes are financially
viable. 2010 American Institute of Physics. doi:10.1063/1.3464755
I. INTRODUCTION
The development of infrastructure is an important factor to sustain economic growth and
power sector is one of the most important constituents of infrastructure. The achievement of
energy security necessitates diversification of the energy resources and the sources of their supply,
as well as measures for conservation of energy. The global electricity generation has more than
doubled in the past two decades due to increasing economic development. Hydropower provides
17% of electricity demand of the world from an installed capacity of about 730 GW.1 Hydropower
stations have inherent ability for instantaneous starting, stopping, and load variations and also help
improve reliability of the power system. It is closely linked to both water management and
renewable energy generation and plays a unique role in sustainable development for providing
safe drinking water and adequate energy supply. Hydropower resources are widely spread through-
out the world and about 70% of economically feasible potential remains to be developed, mostly
in developing countries.2
In addition to power generation, hydropower projects have several ad-
vantages such as flood protection, flow regulation, fossil fuel avoidance, and revenue generation.
These plants have low operation maintenance and replacement cost.3
However, economic and
environmental factors seriously restrict the exploitation of hydropower through conventional large
capacity projects. Due to these constraints, renewable energy resources such as solar, wind, bio-mass, and small hydropower SHP, which India has in abundance, are being considered to meet
the energy demand in an environmentally benign manner. Among all the renewable energy re-
sources, small hydropower, which is defined by different plant capacities in different countries, is
considered as one of the most promising sources. The contribution of SHP is about 1%2% of the
aAuthor to whom correspondence should be addressed. Tel.: 91 1332 285167. FAX: 91 1332 273517. Electronic
addresses: [email protected] and [email protected].
JOURNAL OF RENEWABLE AND SUSTAINABLE ENERGY 2, 043109 2010
2, 043109-11941-7012/2010/24/043109/13/$30.00 2010 American Institute of Physics
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http://dx.doi.org/10.1063/1.3464755http://dx.doi.org/10.1063/1.3464755http://dx.doi.org/10.1063/1.3464755http://dx.doi.org/10.1063/1.3464755http://dx.doi.org/10.1063/1.3464755http://dx.doi.org/10.1063/1.3464755http://dx.doi.org/10.1063/1.34647557/23/2019 Optimize of Low Head Small Hydro Power Project
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total capacity. Technical, economic, and environmental benefits of small hydropower make it an
important future contributor particularly in developing countries such as India, Turkey, Brazil, and
China.4
Hydropower is described as a renewable and sustainable energy resource, meeting global
energy challenges in a reasonable way. Hydropower on a small scale is one of the most cost
effective energy technologies.5,6
In India, plant capacity of up to 25 MW is considered as small
hydropower scheme. The environmental impacts of small hydropower plants are at the lowest
levels compared to other alternative resources.7,8
In India, it has been estimated that a potential of
15 000 MW exists in small hydropower range, out of which only 2045 MW has been installed so
far.9
Large potential of untapped hydroenergy is available in flowing streams, river slopes, canal
falls, drainage works, and irrigation and water supply dams. Most of these hydropower sites come
under low head range, i.e., from 3 to 20 m. Small hydropower schemes are categorized into three
types of schemes, i.e., canal based, run of river, and dam toe. Based on head, these schemes are
defined as high head, medium head, and low head schemes. Low head schemes could be canal
based, run of river, and dam toe, while high and medium head schemes are run of river and dam
based schemes. In the case of high head schemes, there are uncertainties about the geology and
hydrology. Due to these uncertainties, medium and high head schemes are considered site specific.The low head schemes have to handle large quantities of water. Thus, the size of the civil
structures as well as the generating equipment is large. Dam toe low head schemes being planned
on the existing low height dams mainly meant for irrigation systems have established hydrology
and are free from geological and discharge uncertainties. Water availability in rivers is not the
same throughout the year and the maximum availability of water is in the rainy season, which lasts
for 34 months a year. Dams are constructed to store this seasonal water for flood mitigation,
irrigation, and drinking needs. When water flows from dam outlets under pressure, due to the
water level difference between upstream and downstream of the dam, there is a possibility of
power generation. These schemes are known as dam toe hydropower schemes.
It is difficult to estimate the realistic project cost at the preliminary stage to make an invest-
ment decision. A number of investigators tried to establish the methodology for cost estimation of
hydropower schemes based on the existing project data. In low head small hydropower plants, thecost of the power house in civil works and the cost of the turbine in electromechanical works has
been found to be significant. Percentagewise bifurcation of the cost of various components has
been presented and technological aspects were also discussed in the study.10
Gordon11
developed
a simple methodology for checking first order cost of hydropower projects. This methodology was
based on a satisfied analysis of the cost data of 170 projects. In the feasibility stage, accurate
topographical maps, final hydrological studies, detailed geological studies, and sufficient engineer-
ing designs to define the project quantities were suggested to be available. Accuracy of estimates
at this stage is within 15%25%. Gordon11
has developed correlation of the cost of hydropower
projects with respect to head and capacity based on the data available. These correlations are
largely applicable to large hydropower schemes having medium and high heads.
Gordon and Noel12
developed a simple methodology for estimating the likely minimum cost
of small hydropower sites. The study was based on the data of 141 sites. The cost of smallhydropower sites was divided into three components: site costs, equipment cost, and engineering
administration. The relationships developed were based on the generalized conditions and the
specific and unusual circumstances were not considered. These relationships did not account for
specific physical, economic, or business environment of the sites. The methodology can be useful
to discard those sites where cost is higher than the affordable cost of alternative energy.
Literature survey reveals that a number of studies have been carried out in the area of small
hydropower. However, no study was reported so far for cost optimization of low head dam toe
small hydropower installations. Keeping this in mind, the present study was carried out to develop
a methodology for assessment of the cost of such projects.
043109-2 Singal, Saini, and Raghuvanshi J. Renewable Sustainable Energy2, 043109 2010
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II. DAM TOE SHP SCHEMES
A schematic of dam toe SHP scheme is shown in Fig. 1.13
In dam toe schemes, the power
house building is located at the toe of the dam and penstock is taken through the body of the dam.
Basic components of such schemes are categorized into two parts: i civil works andiielectro-
mechanical equipment. The major components of civil works consist of intake, penstock, power
house building, and tail race channel. The electromechanical components are turbines with gov-erning system, generator with excitation system, electrical and mechanical auxiliary, and trans-
former and switchyard equipment. Out of these, hydroturbines play an important role that can be
considered as the heart of a small hydropower station. The selection, type, and specification of
other equipment in the SHP station are dependent on the hydroturbine. The selection of turbine is
governed by head, discharge, capacity, speed, part load efficiency, number of units, and cavitation
characteristics. The size of turbine is defined by its runner diameter. Thevarious turbines consid-
ered for analysis and their part load efficiency are presented in Table I.14
III. COST ANALYSIS
During the investigations, it was observed that the cost of components of civil works as well
as that of electromechanical equipment mainly depends on the installed capacity and head of the
scheme. In order to estimate the cost of various components of low head SHP scheme, correlations
for the cost as a functionof installed capacityand head are developed from the determined values
of cost. Saini and Saini15
and Singal and Saini16
found that the statistical approach can be adopted
for the development of correlations by regression analysis from the determined values.
A. Civil works
For a range of capacity, head, and other related parameters considered under the present study,
cost values are determined for each component based on actual quantities of different items and
prevailing item rates. Correlations for the cost of components of civil works are developed by
FIG. 1. Schematic of typical dam toe SHP scheme.
043109-3 Low-head, dam-toe, SHP projects J. Renewable Sustainable Energy2, 043109 2010
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using the methodology adopted earlier by Singal and Saini.16
It is revealed from the determined
values that the cost is the strong function of capacity Pand headHof a scheme. Therefore, thefunctional relationship for cost per kilowatt C can be written as
C = fP,H. 1
The steps involved for the development of correlation for cost per kilowatt of intake C1 are
shown in Figs.2and 3. The developed correlation is represented by
C1= a1Px1Hy1. 2
Along similar lines, correlations for the cost of other components of civil works such as
penstockC2, power house buildingC3, and tail race channelC4are also developed, as shown
below.
C2= a2Px2Hy2, 3
C3= a3Px3Hy3, 4
TABLE I. Value of part load efficiency of different turbines considered for the analysis.
Serial no. Type of turbines
Efficiency at part load/discharge ratioMaximum
efficiency100% 90% 80% 70% 60% 50%
1 Tubular semi-Kaplan 0.90 0.90 0.90 0.88 0.85 0.82 0.902 Vertical semi-Kaplan 0.89 0.89 0.89 0.87 0.84 0.81 0.89
3 Bulb semi-Kaplan 0.91 0.91 0.91 0.89 0.86 0.83 0.91
4 Tubular propeller 0.89 0.88 0.85 0.80 0.75 0.70 0.89
5 Vertical propeller 0.88 0.87 0.84 0.79 0.74 0.69 0.88
6 Bulb propeller 0.90 0.89 0.86 0.81 0.76 0.71 0.90
7 Tubular Kaplan 0.92 0.92 0.92 0.91 0.90 0.89 0.92
8 Vertical Kaplan 0.91 0.91 0.91 0.90 0.89 0.88 0.91
9 Bulb Kaplan 0.93 0.93 0.93 0.92 0.91 0.90 0.93
1600
1800
2000
2200
2400
2600
2800
3000
1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
Capacity, kW
Costp
erkW,
Rs
FIG. 2. Plot of cost per kilowatt of intake with capacity.
043109-4 Singal, Saini, and Raghuvanshi J. Renewable Sustainable Energy2, 043109 2010
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C4= a4Px4Hy4. 5
The values of the coefficients in Eqs. 2, 3, and 5 are given below. The values of the
coefficients in Eq.4 for the cost of power house building are different, corresponding to layouts
with different types of turbines and generators, as given in Table II,
a1= 17 940, x1= 0.2366, y1= 0.0596,
a2= 7875, x2= 0.3806, y2= 0.3804,
a4= 28 164, x4= 0.376, y4= 0.6240.
B. Electromechanical equipment
A similar methodology used for the development of the correlations for the cost of civil works
has been used to develop the correlations for the cost of different components of electromechani-
cal equipment. The developed correlations for the cost per kilowatt of turbines with governing
systemC5, generator with excitation system C6, electrical and mechanical auxiliary C7, and
transformer and switchyard equipment C8 as a function of head and capacity are represented as
follows:
14500
15000
15500
16000
16500
17000
17500
2 4 6 8 10 12 14 16 18 20
Head, m
CostperkW
/(capacity)-0.2
366
FIG. 3. Plot of cost per kilowatt of intakecapacity0.2366 with head.
TABLE II. Coefficients in cost correlation of power house.
Serial no. Type of turbine
Coefficients in cost correlation
a3 x3 y3
1 Tubular se mi-Kaplan 92 615 0.2351 0.0585
2 Vertical semi-Kaplan 83 406 0.2353 0.0588
3 Bulb semi-Kaplan 76 103 0.2353 0.0586
4 Tubular propeller 91 231 0.2356 0.0588
5 Vertical propeller 89 664 0.2359 0.0591
6 Bulb propeller 72 076 0.2355 0.0588
7 Tubular Kaplan 97 764 0.2356 0.0589
8 Vertical Kaplan 88 631 0.2357 0.0590
9 Bulb Kaplan 79 962 0.2355 0.0588
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C5= a5Px5Hy5, 6
C6= a6Px6Hy6, 7
C7= a7Px7Hy7, 8
C8= a8Px8Hy8. 9
The values of constants and exponents in Eq. 9 are given below,
a8= 18 739, x8= 0.1803, y8= 0.2075.
TABLE III. Coefficients in cost correlation for electromechanical equipment having two generating units.
Serial
no.
Type of
turbine
Type of
generator
Coefficients for cost of electromechanical equipment
Turbine Generator Auxiliary
a5 x5 y5 a6 x6 y6 a7 x7 y7
1
Tubular
semi-Kaplan Synchronous 63 346 0.1913 0.2171 78 661 0.1855 0.2083 40 860 0.1892 0.2118
2
Tubular
semi-Kaplan Induction 63 346 0.1913 0.2171 66 268 0.1882 0.207 35 930 0.1831 0.2098
3
Vertical
semi-Kaplan Synchronous 62 902 0.1835 0.2092 83 091 0.1827 0.2097 42 332 0.1859 0.2084
4
Vertical
semi-Kaplan Induction 62 902 0.1835 0.2092 70 299 0.1826 0.2125 37 171 0.1848 0.2094
5
Bulb
semi-Kaplan Synchronous 67 015 0.1824 0.2092 91 696 0.1893 0.2137 44 044 0.1858 0.2141
6
Bulb
semi-Kaplan Induction 67 015 0.1824 0.2092 78 258 0.1833 0.2091 39 223 0.18 0.1986
7Tubular
propeller Synchronous 61 153 0.1961 0.2111 78 661 0.1855 0.2083 38 328 0.1902 0.2134
8
Tubular
p ro pe ller Ind uctio n 6 1 1 53 0.1961 0.2111 66 268 0.1882 0.207 34 124 0.1897 0.2196
9
Vertical
propeller Synchronous 59 264 0.1817 0.2106 83 091 0.1827 0.2097 39 665 0.1863 0.2082
10
Vertical
p ro pe ller Ind uctio n 5 9 2 64 0.1817 0.2106 70 299 0.1826 0.2125 34 852 01865 0.212
11
Bulb
propeller Synchronous 64 017 0.185 0.2031 91 696 0.1893 0.2137 42 641 0.1929 0.2048
12
Bulb
p ro pe ller Ind uctio n 6 4 0 17 0.185 0.2031 78 258 0.1833 0.2091 37 513 0.1831 0.2119
13
Tubular
Kaplan Synchronous 70 170 0.1853 0.2053 81 881 0.1858 0.2095 41 982 0.187 0.2099
14TubularKaplan Induct ion 70 170 0.1853 0.2053 72 121 0.1868 0.2082 37 168 0.184 0.2156
15
Vertical
Kaplan Synchronous 73 624 0.1872 0.2105 85 377 0.1816 0.2082 44 729 0.1924 0.2166
16
Vertical
Kaplan Induct ion 73 624 0.1872 0.2105 77 693 0.184 0.2096 39 199 0.1805 0.2072
17
Bulb
Kaplan Synchronous 75 048 0.1873 0.2086 99 401 0.1886 0.209 45 326 0.1912 0.2072
18
Bulb
Kaplan Induct ion 75 048 0.1873 0.2086 85 417 0.188 0.2096 40 096 0.1847 0.2156
043109-6 Singal, Saini, and Raghuvanshi J. Renewable Sustainable Energy2, 043109 2010
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The values of constants and exponents in Eqs. 68 are different for different types of
turbines and generators, as given in Table III.
C. Total installation cost
The total project cost includes cost of civil works, cost of electromechanical equipment, costof other miscellaneous items, and other indirect costs. 13% of the cost ofcivil works and elec-
tromechanical equipment has been considered on account of these costs.17
The total installation costs are represented as follows.
i Cost of civil worksRs/kW, Ccd,
=C 1+ C2+ C3+ C4. 10
ii Cost of electromechanical equipmentRs/kW, Ce&m,
=C 5+ C6+ C7+ C8. 11
iii Miscellaneous cost Rs/kW, Cmd,
=0.13Ccd+Ce&m. 12iv Total cost Rs/kW, Cd,
=C cd + Ce&m+ Cmd. 13
Based on the correlations developed for components of dam toe SHP schemes, installation
cost has been determined for such schemes having different types of turbines and generators.
IV. COST OPTIMIZATION
Prior to 1991, small hydropower projects in India were only developed in the government
sector as government departments were the licensee to generate, transmit, and distribute electrical
energy. From 1991 onward, power generation was opened to the private sector as well and
government departments were streamlined as companies. Since then it has become the commercialsector and repayment of investments is of prime concern; therefore, financial analysis has been
attempted to evaluate the schemes for evolving an optimum solution. In this context, financial
analysis has been carried out to evaluate various layouts. An important part of establishing finan-
cial feasibility is the anticipated borrowing cost. The cost of capital is the return expected by
potential investors and other market and economic costs. The costs are the sum of the real interest
rate that compensates the lender for surrendering the use of funds, the purchasing power, the risk
premium that compensates for expected inflation, the business and financial risk, and the market-
TABLE IV. Values of parameters considered for financial analysis Refs.1921.
Serial no. Parameters Value
1 Annual interest rate 11%2 Annual depreciation 3.4%
3 Annual operation and maintenance cost 1.5%
4 Selling price of electricity Rs 2.50/kW h
5
Annual escalation on operation and maintenance
expenses and electricity prices 4%
6 Life of plant considered for analysis 25 yr
7 Construction period 2 yr
8 Investment in first year 77%
9 Investment in second year 23%
10 Debt equity ratio 70:30
043109-7 Low-head, dam-toe, SHP projects J. Renewable Sustainable Energy2, 043109 2010
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ability risk associated with low liquidity of long-term debt. A financially feasible SHP project,
where necessary funds are available to pay for it through sale of electricity generated, does not
mean that the project is the best of all the available alternatives or that the proposed execution is
appropriate. Besides, an economically feasible project cannot be financed. Also, the debt limit of
an agency or organizations jurisdiction can prohibit borrowing of additional funds to finance a
project.
Financial analysis includes cost of operation and maintenance, administration, and replace-
ment. Each cost included in the annual cost analysis is regarded to be either a constant value for
the life of the project or treated as an equivalent uniform annual cost by using a uniform series of
annual payments reflecting the life of the project and the cost of money. If the owner finances the
project from internal funds, then the annual cost is based on a required rate of return rather than
the interest rate of the borrowed money.
The layouts of SHP schemes have been evaluated for cost optimization, considering type ofturbine, type of generator, and plant load factor. The efficiencies of different turbines and genera-
tors are different, as given in Table I, which affect the energy generation. To arrive at consistent
values for both benefits and costs so that they can be compared, the present value criterion is
20000
30000
40000
50000
60000
70000
80000
1000
3000
5000
7000
9000
11000
13000
15000
17000
19000
21000
23000
25000
Capacity (kW)
CostperkW
(Rs.)
Head 3 m
Head 10 mHead 20 m
FIG. 4. Dam toe SHP scheme with two units.
FIG. 5. Comparison of the total cost per kilowatt as analyzed with the cost data collected for the existing dam toe schemes.
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adopted. The present value has been determined at the time of first expenditure of the future
stream of benefits based on a fixed value of discount rate, considered as 11% in the present stud y.The present valuePV of the project has been computed by adopting the formula given below,
18
PV =i=1
n
CFi1 + di
+ Sn1 + dn
, 14where PV is the present value, CFiis the cash flow in year i starting with the initial investment, Snis the salvage value, D is the discount rate, and n is the number of years of the projects.
The financial feasibility with emphasis on internal financial rate of return has been attempted.
Financial internal rate of return FIRR is the discount rate at which the present value of benefits
becomes equal to the present value of cost, i.e., expenditure. FIRR has been determined based on
the annual expenditure and annual return from sale of electricity generated from the power plant
for 25 years after the plant is put into operation by using an iterative technique. The project havinga maximum FIRR value is the optimum. The financial parameters used for the calculation of FIRR
are given in TableIV.The procedure adopted for the computation of FIRR is discussed as follows:
i Determine the installation cost using correlationsEq. 13 for known values of head andinstalled capacity.
ii Determine the annual energy by using the equation
E = P 8760 T g PL, 15
where E is the energy in kW h, P is the installed capacity in kW, T is the efficiency ofturbine, g is the efficiency of generator, and PL is the plant load factor.
0
2
4
6
8
10
12
14
16
18
20
TS&Syn
.
TS&
Ind.
VS&Sy
n.
VS&
Ind.
BS &Sy
n.
BS&
Ind.
TP&Syn
.
TP&I
nd.
VP&Sy
n.
VP&
Ind.
BP&Sy
n.
BP&
Ind.
TKSy
n.
TK&
Ind.
VK&Sy
n.
VK&
Ind.
BK&Sy
n.
BK&
Ind.
Type of turbines and generators
FIRR
50% 60% 70% 80% 90%
T - Tubular P - P ropellor
B - Bulb S - Semikaplan
V - Vertical K - Kaplan
Ind. - Induction Syn. - Synchronous
Plant load factor
FIRR(%)
FIG. 6. FIRR for dam toe scheme of 2000 kW capacity at 3 m head having different turbines and generators at different
load factors.
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iii Determine the annual cost and generation cost by using Eqs. 16 and 17, consideringoperation and maintenance O&M cost including insurance, depreciation, and interest onthe capital borrowed based on the values of these parameters as given in Table IV.
Annual cost, Ca= Co&m+ Cd+ Ci , 16
Generation cost, Cg= Ca/E, 17
where Co&m is the operation and maintenance cost, Cd is the depreciation cost, Ci is theannual interest, and E is the annual energy.
iv Determine FIRR values based on installation cost, annual cost, annual energy, and selling
price of electricity by an iterative technique.
V. SENSITIVITY ANALYSIS
In hydropower projects, there are uncertainties on account of water availability that affect the
availability of energy. Thus, there is an uncertainty in projection of the benefits from the project
and the other uncertainty factor is the cost estimation. The cost of the project depends on location,
construction period and variation in cost of materials, availability of construction equipment, and
variation in labor cost. The project cost estimates are subject to a considerable degree of variation
and fluctuation. The benefits also have a high degree of uncertainty. Therefore, projects are tested
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
TS&S
yn.
TS&I
nd.
VS&S
yn.
VS&I
nd.
BS &S
yn.
BS&I
nd.
TP&S
yn.
TP&I
nd.
VP&S
yn.
VP&I
nd.
BP&S
yn.
BP&I
nd.
TKSy
n.
TK&I
nd.
VK&S
yn.
VK&I
nd.
BK&S
yn.
BK&I
nd.
Type of turbines and generators
FIRR
50% 60% 70% 80% 90%
T - Tubular P - P ropel lor
B - Bulb S - Semikaplan
V - V ert ic al K - K aplan
Ind. - Induction Syn. - Synchronous
Plant load factor
FIRR(%)
FIG. 7. FIRR for dam toe scheme of 10 000 kW capacities at 20 m head having different turbines and generators at
different load factors.
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for sensitivity to determine the effect of changes in the levels of the most critical variables. In
order to evaluate the optimuminstallation, sensitivity analysis has been carried out by taking the
following into considerations:18
i installation cost increased by 10%;ii benefits, i.e., availability of energy reduced by 10%; andiii combined impact of both cost and benefits, i.e., installation cost up by 10% and benefits
down by 10%.
Considering these conditions, FIRR has been computed using the methodology discussed
earlier in Sec. IV to compare the results under different conditions.
VI. RESULT AND DISCUSSION
In the present study, low head dam toe SHP schemes having two generating units have been
considered for analysis. As discussed above, the cost for different components of low head dam
toe SHP scheme has been computed based on the actual quantities of various items and their
prevailing prices. The computed cost data were used to develop the correlations based on the
available method.15,16
The process for developing correlation has been shown in Figs. 2 and 3.
Based on the correlation developed, installation cost has been determined for different heads and
capacities, as shown in Fig. 4. In order to verify the validity of the developed correlations, a
comparison was made between cost determined by using correlation and cost data collected for
similar plants installed recently. As shown in Fig. 5, it has been found that there is a maximum
deviation of11%. This shows the accuracy of the developed correlation. The factors responsible
for this variation can be geological/soil conditions, type of turbine, type of generator, and location
of site.
Based on the determined installation cost and parameters given in TableIV,financial analysis
has been carried out to determine the financial internal rate of return for different layouts using
different types of turbines and generators at different load factors. FIRR values for different
layouts of dam toe schemes having capacity of 2000 kW at 3 m head and 10 000 kW at 20 m head
have been considered. It is seen from Figs.6 and 7 that at 50% load factor, a bulb turbine with a
Kaplan runner is the optimum layout having maximum FIRR, i.e., 3.80% and 15.50%, respec-
tively. At 60%, 70%, and 80% load factors, a tubular turbine having a semi-Kaplan runner is found
to be the optimum layout with maximum FIRR values. At 90% load factor, a tubular turbine with
a propeller runner is found as the optimum layout with maximum FIRR value. To account for
TABLE V. Financial internal rate of return % at different load factors under different conditions.
Serial no. Conditions
Load factor
50% 60% 70% 80% 90%
At 3 m head and 2000 kW capacity1 Normal condition 3.80 7.50 11.00 14.00 16.60
2 Installation cost increased by 10% 2.03 5.78 9.20 12.11 14.60
3 Generation reduced by 10% 1.84 5.60 9.02 11.92 14.39
4
Installation cost increased by 10% and generation
reduced by 10% 0.06 3.86 7.29 10.13 12.52
At 20 m head and 10 000 kW capacity
5 Normal condition 15.50 19.70 24.30 28.50 32.34
6 Installation cost increased by 10% 13.62 17.56 21.89 25.87 29.46
7 Generation reduced by 10% 13.43 17.34 21.64 25.60 29.16
8
Installation cost increased by 10% and generation
reduced by 10% 11.59 15.34 19.41 23.13 26.48
043109-11 Low-head, dam-toe, SHP projects J. Renewable Sustainable Energy2, 043109 2010
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uncertainties, sensitivity analysis has been carried out by escalating installation cost and/or reduc-
ing energy generation benefits. The determined values of FIRR under these conditions are given
in TableV.It is seen that the layouts having higher capacities and head are financially viable at all
load factors in all conditions, while layouts having smaller capacities and lower heads are finan-
cially viable at load factors more than 70% in normal conditions and at 90% in extreme
conditions.
VII. CONCLUSIONS
Financial feasibility quantifies a projects ability to obtain funds for implementation and
repayment of funds on a self-liquidating basis. In the present study, methodology to determine the
optimum layout of dam toe SHP schemes has been evolved. It has been found that at a higher load
factor, i.e., 90%, a tubular turbine with a propeller runner is the optimum layout with maximum
FIRR value. At 60%, 70%, and 80% load factors, a tubular turbine having a semi-Kaplan runner
is the optimum layout, while a bulb turbine with a Kaplan runner is the optimum layout at 50%
load factor. Sensitivity analysis shows that the layouts having higher capacities have a financial
internal rate of return values higher than the interest rate. Therefore, these sites are considered to
be financially viable at all load factors under all conditions.
Nomenclature
a1 a8 Coefficients
Ca Annual cost, Rs
Cd Total cost per kilowatt, Rs
Cg Generation cost, Rs
Ci Interest cost, Rs
C1 Cost per kilowatt of intake, Rs
C2 Cost per kilowatt of penstock, Rs
C3 Cost per kilowatt of power house building, Rs
C4 Cost per kilowatt of tailrace channel, Rs
C5 Cost per kilowatt of turbines with governing system, RsC6 Cost per kilowatt of generator with excitation system, Rs
C7 Cost per kilowatt of electrical and mechanical auxiliary, Rs
C8 Cost per kilowatt of transformer and switchyard equipment, Rs.
Ccd Cost per kilowatt of civil works, Rs
Ce&m Cost per kilowatt of electromechanical equipment, Rs
Cmd Cost per kilowatt of miscellaneous items, Rs
CFi Cash flow in ith year
D Discount rate
E Annual energy generation in kW h
g Efficiency of generatorT Efficiency of turbine
FIRR Financial internal rate of return, %
H Rated net head in meter
kW Kilowatt
MW Megawatt
M Meter
N Last year of cash flow
P Rated output power, kW
PL Load factor
PV Present value
Rs Indian rupees 1 US $=45 Indian Rs
Sn Salvage value
043109-12 Singal, Saini, and Raghuvanshi J. Renewable Sustainable Energy2, 043109 2010
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SHP Small hydropower
x1 , . . . , x8 Coefficients
y1 , . . . , y8 Coefficients
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043109-13 Low-head, dam-toe, SHP projects J. Renewable Sustainable Energy2, 043109 2010
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